Updated Sep 5, 2023 - Energy & Environment

The link between extreme weather in Greece, U.K. and Spain

Photo of overturned, damaged cars during the floods in Spain during early Sept. 2023

Several vehicles piled up due to flooding after being swept away by the water, on Sept. 4. Photo: Diego Radames/Europa Press via Getty Images

Extremely heavy rains and associated flooding are worsening in central Greece, and are connected to a potentially record-breaking early September heat wave in London and Paris.

Why it matters: These extreme events, along with flooding that struck Spain Sunday into early Monday, are each tied to an unusually stuck weather pattern, with elevated water temperatures in the Mediterranean adding to the trouble.

Zoom in: For the past few days, computer models have zeroed in on central Greece as a likely location of potentially disastrous amounts of rainfall, on the order of between 20 to 40 inches or more in just a few days' time.

  • Torrential rains have indeed materialized and already turned deadly. It's been fed by added moisture and energy from the warm Mediterranean, and directed inland and into high elevations by the air rotating around an intense storm system spinning to the country's southwest.
  • In Zagora, a total of 30 inches of rain has reportedly fallen so far, with 25 inches falling since midnight Tuesday.

The storm, known regionally as Daniel, has already dumped a reported two feet of rain in central Greece, focused on the Tessaly region. According to the AP, traffic has been banned in the town of Volos, the island of Skiathos and the mountain region of Pilion until the rain subsides.

Context: Heavy rainfall events are occurring more frequently worldwide, and also are becoming more severe, which scientists have linked to the burning of fossil fuels.

  • A hotter atmosphere and oceans adds more moisture and energy to storm systems, studies show, enabling them to produce greater amounts in short time spans.
  • This could turn into one of Europe's worst flood disasters in decades, depending if certain forecast scenarios come to fruition.

Of note: The heavy rainfall in Greece, which is already exceeding the typical amount of precipitation Athens sees in an entire year, is part of a severe bout of weather whiplash.

  • It was only a few days ago that the biggest extreme weather concern in Greece were raging wildfires, with crews battling the EU's largest blaze on record.
Image of a Tweet illustrating the concept of an Omega Block.

The big picture: The weather pattern across Europe features a stuck weather pattern, known as an "Omega Block," that is associated with extreme outcomes.

  • Currently, the jet stream is taking a deep plunge southward across Spain, then turning northward and curving across the top end of the U.K., and back down south into Greece, in a formation that looks like the Greek letter Omega.
  • Last week, a stalled storm system caused widespread, deadly flooding in Spain, particularly in Toledo, south of Madrid.
  • This pattern is also allowing a heat dome to build across England and northern France, potentially leading to some of their hottest weather of the year so far, though it may fall short of breaking all-time temperature records.
  • Temperatures in London are forecast to exceed 30°C (86°F) on Wednesday.

What we're watching: More rain is forecast for Greece as the storm system barely budges, continuously tapping the unusually hot waters in the Mediterranean and directing that moisture into Greece's northwest.

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